[MERGE] Fix test suite regression on OSX in TestReadMergeableFromUrl.test_smart_server_connection_reset.

[Andrew Bennetts]

Vincent Ladeuil wrote:
[...]
> +            if len(e.args) and e.args[0] is errno.ECONNRESET:

In addition to my other comments, don't use “is” to compare these
integers, just use “==”.  It'll probably work all the time with all
current implementations of CPython, but we shouldn't be relying on that.

-Andrew.